The present invention relates generally to envelopes and, more particularly, to a variable size envelope with a single closure flap that may be selectively folded along two different fold lines to provide two different size envelopes, the smaller envelope being of uniform thickness to facilitate processing through automatic mechanical sheet feed printing equipment, laser printing equipment and feed through copy machines.
In the past, envelopes of variable size have been difficult to process through automatic mechanical printing equipment, laser printing equipment and copying machines because the envelopes were either too big to send through such machines when folded into a larger size, or difficult to process when folded into a smaller size. For example, German Patent No. 631,006, issued to Bassler, et al. on June 10, 1936, discloses an envelope with a closure flap which may be folded along two different lines and sealed to provide envelopes of two different sizes. However, when folded into smaller size envelopes, the envelope disclosed in this patent presents folds through two thicknesses of material and overlapping portions near the top of the envelope which lead to an envelope of uneven thickness difficult to process through automatic mechanical printing equipment, laser printing equipment and copying machines. The expanding envelope disclosed in U.S. Pat. No. 3,063,618, issued to Berkowitz on Nov. 13, 1962, presents the same problems because it is not of uniform thickness when folded and has overlapping portions.